This invention relates to a steering control system for an unmanned vehicle.
A programmed turning system employing a trapezoid function turning program as shown in FIG. 1 is known in the art as a steering control system in which at the intersection of guide cables an un-manned vehicle is turned so as to be shifted from one guide cable to the other guide cable.
In this conventional system, after the guide travelling operation of the vehicle along one of the guide cables has been released, a programmed turning operation of the vehicle is carried out for the other guide cable in accordance with a vehicle turning program. When the turning operation is finished (or the steering angle becomes zero), the guide travelling operation along the other guide cable is effected immediately. In this system, it is difficult to smoothly switch the programmed turning operation over to the guide travelling operation. Therefore, the conventional system is disadvantageous in that after the programmed turning operation has been switched over to the guide travelling operation along the other guide cable, the vehicle is liable to move along a wandering course.
In view of the foregoing, an object of this invention is to provide a steering control system for an unmanned vehicle in which the programmed turning operation can be smoothly changed over to the guide travelling operation.
It is another object of the invention to provide a steering control system for an unmanned vehicle which is capable of transferring the vehicle smoothly between a main cable and any one of cables intersecting with the main cable by utilizing the above described steering control system.
In this invention, the conventional system in which th programmed turning operation is switched over to the guide travelling operation when completed is not employed. That is, in the steering control systems according to the invention, irrespective of the completion of the programmed turning operation (even during the programmed turning operation, or even if it passes more or less after the completion of the progammed turning operation), the programmed turning operation is switched over to the guide travelling operation when the vehicle reaches the guide cable, thereby to smoothly change the operations.
In the following description of this invention, the term "turning angle" as used herein is intended to mean the amount of change in direction of the vehicle with respect to the state of the vehicle which is about to start the turning operation. The term "predetermined turning angle" is intended to mean a turning angle required for the vehicle to shift to the other guide cable in such a manner that the vehicle is in parallel with the other guide cable. Furthermore, a turning program such that a programmed turning is completed with the vehicle shifted onto the other cable, being in parallel with the other cable, will be referred to as "a turning program with the predetermined turning angle". In addition, a turning program such that a program turning is completed before the vehicle is shifted onto the other cable will be referred to as "a turning program having a turning angle less than the predetermined turning angle".